This was a trial of vitamin A therapy in a single patient, a 4 year old boy with autism. The parents had recorded repeated behavioral changes following vitamin A. The objectives were to determine if there were measurable changes in behavior and metabolites of vitamin A. In two one- week sessions in the PCRU, the subject was administered vitamin A from 5,000 to 50,000 IU orally on alternate days in randomized placebo- controlled fashion. Behavioral assessments took place twice daily by experienced behavioral psychologists and blood samples were collected for serum caratenoids every 6 hours. Results showed no adverse effects of vitamin A and no correlation of behaviors to the levels of vitamin A administered. Serum retinol and retinyl palmitate increased normally in proportion to each dose of vitamin A the patient received. There was no evidence for behavioral effects or abnormal metabolism of vitamin A in this patient with autism.